Transcript Document

Designing with 802.15.4 and ZigBee
Industrial Wireless Applications Summit
San Diego, California
9 March 2004
Jon Adams
Chairman
ZigBee Qualification Group
ZigBee Alliance
Director, Radio Technology and Strategy
Motorola Wireless and Mobile Systems Group
Tempe, Arizona
[email protected]
+1 480.413.3439 Office
Copyright 2004 The ZigBee Alliance, Inc.
1
IEEE 802.15.4 Basics
• 802.15.4 is a simple packet data protocol for lightweight
wireless networks
– Channel Access is via Carrier Sense Multiple Access with collision
avoidance and optional time slotting
– Message acknowledgement and an optional beacon structure
– Multi-level security
– Three bands, 27 channels specified
• 2.4 GHz: 16 channels, 250 kbps
• 868.3 MHz : 1 channel, 20 kbps
• 902-928 MHz: 10 channels, 40 kbps
– Works well for
• Long battery life, selectable latency for controllers, sensors, remote
monitoring and portable electronics
– Configured for maximum battery life, has the potential to last as
long as the shelf life of most batteries
Copyright 2004 The ZigBee Alliance, Inc.
2
PHY Performance
802.15.4 has excellent
performance in low
SNR environments
Bluetooth
Copyright 2004 The ZigBee Alliance, Inc.
3
IEEE 802.15.4 MAC Overview
•
Employs 64-bit IEEE & 16-bit short addresses
– Ultimate network size can reach 264 nodes (more than we’ll probably
need…)
– Using local addressing, simple networks of more than 65,000 (2^16) nodes
can be configured, with reduced address overhead
•
Three devices specified
– Network Coordinator
– Full Function Device (FFD)
– Reduced Function Device (RFD)
•
•
•
•
•
•
•
Simple frame structure
Reliable delivery of data
Association/disassociation
AES-128 security
CSMA-CA channel access
Optional superframe structure with beacons
Optional GTS mechanism
Copyright 2004 The ZigBee Alliance, Inc.
4
Data Frame format
•
•
•
•
•
One of two most basic and important structures in 15.4
Provides up to 104 byte data payload capacity
Data sequence numbering to ensure that packets are tracked
Robust structure improves reception in difficult conditions
Frame Check Sequence (FCS) validates error-free data
Copyright 2004 The ZigBee Alliance, Inc.
5
Acknowledgement Frame Format
• The other most important structure for 15.4
• Provides active feedback from receiver to sender that
packet was received without error
• Short packet that takes advantage of standardsspecified “quiet time” immediately after data packet
transmission
Copyright 2004 The ZigBee Alliance, Inc.
6
MAC Command Frame format
• Mechanism for remote control/configuration of
client nodes
• Allows a centralized network manager to
configure individual clients no matter how
large the network
Copyright 2004 The ZigBee Alliance, Inc.
7
Beacon Frame format
•
•
•
Beacons add a new level of functionality to a network
Client devices can wake up only when a beacon is to be broadcast,
listen for their address, and if not heard, return to sleep
Beacons are important for mesh and cluster tree networks to keep all
of the nodes synchronized without requiring nodes to consume
precious battery energy listening for long periods of time
Copyright 2004 The ZigBee Alliance, Inc.
8
ZigBee is Mesh Networking
ZigBee Coordinator (FFD)
ZigBee Router (FFD)
ZigBee End Device (RFD or FFD)
Mesh Link
Star Link
Copyright 2004 The ZigBee Alliance, Inc.
9
Motorola 802.15.4 / ZigBee™ solution
• Features
– 2.4 GHz Band, -92 dBm RX sensitivity at 1% PER
• IEEE requirement is at least –85 dBm
– Power supply 2.0-3.6 V w/ on-chip regulator, logic interface 1.7 to
3.3
• Runs off a single Li or 2 alkaline cells
– Complete RF transceiver data modem – antenna in, fully
packetized data out
– Data and control interface via standard SPI at 4 MHz minimum
– 802.15.4 MAC supplied
– Four new Motorola HCS08 MCUs will interoperate with the data
modem chip
• Often 802.15.4 functionality can be added to existing systems simply
by including the modem chip and reprogramming an existing MCU that
may already be in the application
– HC08 RAM/FLASH configurations from 384B/4kB to 2kB/60kB
depending upon application SW needs
Copyright 2004 The ZigBee Alliance, Inc.
10
System Simplicity and Flexibility
Motorola RF Packet Radio
Motorola 8-Bit MCU
Copyright 2004 The ZigBee Alliance, Inc.
11
Motorola’s 802.15.4 Platform Advantages
•
One-Stop-Shop Solution
– Single source for platform solution
• Integrated Circuits, Reference Designs, Modules, Stack Software, Development
Systems
•
Key technology enhancements provide for a superior solution
– Excellent adjacent channel rejection
• No external filtering required under most conditions
– High Sensitivity Radio Solution
• 7 dBm better than spec – longer range
– Extended Temperature Operating Range
• -40°C to +85°C for industrial and automotive applications
– Operating voltage range optimized for alkaline or lithium primary cells
• 2.0 Vdc to 3.6 Vdc, disposable
–
–
Nearly 100% of available battery life whether Alkaline or Lithium
Normal 2.7v EOL silicon systems can only get perhaps 30% of available alkaline battery
energy
– Adjustable TX Output power
• Improved coexistence for short range applications
•
IEEE Participation and ZigBee™ Alliance leadership
– Technology and standards driver
– Early access to new technology
Copyright 2004 The ZigBee Alliance, Inc.
12
15.4/ZigBee and Bluetooth
• Instantaneous Power Consumption
– 15.4 Transceivers are “similar” to Bluetooth Transceivers
• 802.15.4
– O-QPSK with shaping
– Max data rate 250kbps over the air
– 2Mchips/s over the air Direct Sequence Spread Spectrum (62.5ksps*32
spread)
– -92 dBm sensitivity nominal
– 40ppm xtal
• Bluetooth
– FSK
– Max data rate 720kbps over the air
– 1Msps over the air Frequency Hop Spread Spectrum (79 channels @ 1600
hps)
– -83 to -84 dBm sensitivity nominal
– 20ppm xtal
• Instantaneous power consumption will be similar for the raw
transceivers without protocol
• Bluetooth’s FHSS makes it impractical to create extended
networks without large synchronization cost
Copyright 2004 The ZigBee Alliance, Inc.
13
15.4 Protocol Built for the Mission
• 15.4 Protocol was developed for very different reasons than
Bluetooth
– 802.15.4
• Very low duty cycle, very long primary battery life applications as well
as mains-powered
• Static and dynamic mesh, cluster tree and star network structures with
potentially a very large number (>>65534) of client units, low latency
available as required
• Ability to remain quiescent for long periods of time without
communicating to the network
– Bluetooth
• Moderate duty cycle, secondary battery operation where battery lasts
about the same as master unit
• Wire replacement for consumer devices that need moderate data rates
with very high QoS and very low, guaranteed latency
• Quasi-static star network structure with up to 7 clients (and ability to
participate in more than one network simultaneously)
• Generally used in applications where either power is cycled (headsets,
cellphones) or mains-powered (printers, car kits)
• Protocol differences can lead to tremendous optimizations in
power consumption
Copyright 2004 The ZigBee Alliance, Inc.
14
Home/Light Commercial Spaces
Copyright 2004 The ZigBee Alliance, Inc.
15
Industrial/Commercial Spaces
•
•
•
•
•
•
•
•
•
Warehouses, Fleet management,
Factory, Supermarkets, Office
complexes
Gas/Water/Electric meter, HVAC
Smoke, CO, H2O detector
Refrigeration case or appliance
Equipment management services &
Preventative maintenance
Security services
Lighting control
Assembly line and work flow,
Inventory
Materials processing systems (heat,
gas flow, cooling, chemical)
Temp.
Sensor
Database
Gateway
Energy, diagnostics, e-Business
services
•
Gateway or Field Service links to
sensors & equipment
–
•
Monitored to suggest PM, product updates,
status changes
Nodes link to PC for database storage
–
–
PC Modem calls retailer, Service Provider, or
Corp headquarters
Corp headquarters remotely monitors assets,
billing, energy management
Field Service
or mobile
worker
Security
Sensor
Mfg Flow
Back End
Server
Telephone
Cable line
Materials
handling
HVAC
Copyright 2004 The ZigBee Alliance, Inc.
16
Service
Provider
Corp
Office
Retailer
Peel-n’-Stick Security Sensors
• Battery Operation
– 2 AA Alkaline or 1 Li-AA
cell
• 802.15.4/ZigBee Mode
– Non-beacon network
environment
• Sensor process
Vcc
SPI
4
– RC Oscillator waking up
MCU and doing network
check-in at some interval
802.15.4
XCVR CLK
OSC1
IRQ
• Many security systems
have between ~10
second and ~15 minute
requirement
16.000MHz
– On a sensor event,
device immediately
awakens and reports in
to network
Copyright 2004 The ZigBee Alliance, Inc.
17
SPI
Security
Sensor
Vcc
MCU
3Vdc
Security Sensor Timing
Battery-Powered
Sensor
Mains-Powered
Router
Interval timer
expires: Wake Up
Check-in only
~1640µs
Event and Get Data
~2300µs
256µs
CCAx2
192µs
RX>TX
~650µs
TX
RX
192µs
TX>RX
RX>TX
~350µs
ACK RX
ACK TX
OPT: Pending ON
~650µs
RX Data
TX Data
Set Interval timer
Sleep
Copyright 2004 The ZigBee Alliance, Inc.
18
802.15.4 Security Sensor
Any check-in interval
exceeding ~14 sec allows
sensor to surpass alkaline
battery shelf life
Only at 15-min interval
does BT reach battery
shelf life
Copyright 2004 The ZigBee Alliance, Inc.
19
Body-Worn Medical Sensors
• Heartbeat Sensor
– Battery-operated using
CR2032 Li-Coin cell
• 802.15.4/ZigBee Mode
heartbeat
GTS
– Network environment using
Guaranteed Time Slot
(GTS)
– Network beacons occurring
either every
Beacon
time
• 960ms or 61.44s (closest
values to 1 and 60 s)
• Sensor has two ongoing
processes
Vcc
– Heartbeat time logging
– Transmit heartrate and
other information (8 bytes
total)
Vcc
802.15.4
XCVR
SPI
IRQ/
RESET
• Instantaneous and average
heart rate
• Body temperature and
battery voltage
16.000MHz
Copyright 2004 The ZigBee Alliance, Inc.
20
4
3Vdc
SPI
MCU
INT
OSC1
OSC2
32.768kHz
IRQ
Heartbeat
Sensor
802.15.4/ZigBee vs Bluetooth
At beacon interval ~60s,
15.4/ZigBee battery life
approx 416 days
802.15.4/ZigBee more
battery-effective at all
beacon intervals greater
than 0.246s
At beacon interval ~1s,
15.4/ZigBee battery life 85
days
Bluetooth 30 days
(park mode @ 1.28s)
Copyright 2004 The ZigBee Alliance, Inc.
21
Summary
• IEEE 802.15.4 and ZigBee
– Designer concentrates on end application
• Silicon vendors and ZigBee Alliance take care of
transceiver, RF channel and protocol
– Reliable and robust communications
– Flexible network architectures
– Very long primary battery life (months to
years to decades)
– Very inexpensive Bill Of Materials
– Low system complexity for the OEM
• More Information
– Motorola: www.motorola.com/zigbee
– ZigBee: www.zigbee.org
Copyright 2004 The ZigBee Alliance, Inc.
22